Reflections from nonmetallic surfaces such as glass, lacquer, plastic or liquid, result in polarization of the reflected light. Specular glare can be the result of uncontrolled ambient light, but is more often created by the light source chosen for illumination. If the subject is partially obscured by unwanted reflection, a polarizing filter can reduce or eliminate the problem. Glare can be decreased by rotating the filter mounted on the lens. Best results are achieved when a polarizer is used over the lens in conjunction with a polarizer film over the light source.